利用Cherenkov信号进行空间高能中微子测量的潜力
The Potential of Spaced-based High-Energy Neutrino Measurements via the Airshower Cherenkov Signal
摘要：
未来的天基实验，如OWL和JEM-EUSO，将观察大气和陆地上的大型中微子目标。由于通过空气荧光观测空气簇射的能量阈值略高于10^19 eV，因此观测与GZK效应相关的宇宙成因中微子通量的潜力有限。然而，与空气簇射相关的前向切伦科夫信号可以在低得多的能量下观察到。开发了一种模拟，以确定切伦科夫信号强度和近地轨道上向上移动的空气簇射的空间范围。一个地球中的τ中微子相互作用模型被用来确定产生τ轻子的相互作用的事件率，τ轻子将诱导一个向上移动的空气簇射，可由天基仪器观察到。地球对中微子的衰减效应迫使观测地球的临边时，必须在高于OWL切伦科夫能量阈值（约10^16.5 eV）的情况下观测到nu_tau诱导的切伦科夫空气簇射信号。此外，中微子衰减将有效的地球中微子目标面积限制在约3 × 10^5 km^2，能量为10^17 eV，轨道为1000 km，仪器全视场为45度。根据宇宙成因中微子通量的两种不同模型，假设中微子振荡和10%的观测占空比，这转化为可观测的宇宙成因中微子事件率约为1/年。
英文摘要：
Future space-based experiments, such as OWL and JEM-EUSO, view large atmospheric and terrestrial neutrino targets. With energy thresholds slightly above 10^19 eV for observing airshowers via air fluorescence, the potential for observing the cosmogenic neutrino flux associated with the GZK effect is limited. However, the forward Cherenkov signal associated with the airshower can be observed at much lower energies. A simulation was developed to determine the Cherenkov signal strength and spatial extent at low-Earth orbit for upward-moving airshowers. A model of tau neutrino interactions in the Earth was employed to determine the event rate of interactions that yielded a tau lepton which would induce an upward-moving airshower observable by a space-based instrument. The effect of neutrino attenuation by the Earth forces the viewing of the Earth's limb to observe the nu_tau-induced Cherenkov airshower signal at above the OWL Cherenkov energy threshold of ~10^16.5 eV for limb-viewed events. Furthermore, the neutrino attenuation limits the effective terrestrial neutrino target area to ~3x10^5 km^2 at 10^17 eV, for an orbit of 1000 km and an instrumental full Field-of-View of 45 degrees. This translates into an observable cosmogenic neutrino event rate of ~1/year based upon two different models of the cosmogenic neutrino flux, assuming neutrino oscillations and a 10% duty cycle for observation.
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